Process of precipitating aluminium compound



M. 0. SEM.

PROCESS OF PRECIPITATING ALUMINIUM COMPOUND-S.

APPLICATION FILED APR. 23, 1918.

Patented June 28, 1921.

Ovrom S em 98 rm mh mm 6 VM n I flWM Aflorneys v trolysis the reductiontaking place at the.

pNlTE/D STATES.

PATENT OFFICE.

MA'l I-IIAS OVROM SEM, 0F GHRISTIANIA, NORWAY, ASSIGNbR- TO DET NORSKEAKTIESELSKAB FOR ELEKTROKEMISK 'INDUSTRI, 0F CHIRIST'IANIA, NORWAY..

PROCESS OF IPRECIPITATING ALUMINIUM COMPOUND.

T 0 all w ham zit may concern:

Be it known that l, MATHIAs OvRoM SEM, a subject of Norway, and aresident of Christiania, Kingdom of Norway, have invented certain newand useful Improvements in position of minerals containing aluminium bymeans of acid. Decomposition by means of an alkali is generally used inthe production of aluminium compounds. l have however found a simplemethod fo precipitating aluminium compounds from solutions containingaluminium combined with a mineral acid. 1 cause a precipitation ofaluminium compounds by means of elec-- trolysis. The electrolysis ispreferably carried out in a suitable vessel divided into anode andcathode compartments by a porous diaphragm. Preferably an insolubleanode is employed and a small amount of alkali salts isadded to theelectrolyte.

When electrolysis is started aluminium hydrate, or in a sulfate solutionbasic 3111- minium sulfate containing varying amounts of SO willprecipitate at the cathode.

Tn neutral solutions which in themselves have no oxidizing effect theprecipitate -ob-' tained will be practically free from iron for theknown reason. that ferrous iron will not precipitate as long as anexcess of aluminium compounds is present in the solution, and because ofthe hydrogen evolved at the i v cathode ferric iron originally present"will be reduced and kept in the ferrous state or precipitated on thecathode as metallic iron.

On account of their low content of iron,

aluminium compounds precipitated as'above described are very welladapted for the man'- ufacture of aluminium and for similar purposeswhere a great purity is required.

If a nitric acid solution is used in the eleccathode will result in theformation of ammonia from nitric acid. The ammonia Wlll specification ofLetters .Patent. Patented June 28, 1921, Application filed April 23,1918. Serial No. 230,250.

tion process and use it for the decomposition of new amounts of rawmaterial. But I, have found that if the raw material used. is fairlyeasily soluble as is the case with bauxite and some silicates such aslabradorite, I can suspend the raw material in the anode compartment andit will then become dissolved as soon as sufficient acid is liberated,without special concentration of the acid.

As the raw materials used always contain other soluble compounds thanaluminium compounds, these will combine with an equivalent amount of theacid used and must from time totime be removed from the process in theform of salts. In this case an amount of acid corresponding to thatremoved in the form of salts must be added to the process.

I have found that my above described method may be carried outcontinuously and that it is especially. suited for minerals of ment.Therefore aluminium must be supplied to the cathode compartment by othermeans. Also from time to time the undissolved residue from therawmaterial must be removed from the anode compartment.

. Inthe following specific example, I will illustrate the preferred wayof carrying out my process by using a sulfuric acid solution, referencebeing had to the accompanying drawing forming part of this applicationand diagrammatically" illustrating an electrolytic vat in verticalsection, but t 1s of a diaphragm B of the type ordinarily used for suchpurposes, cocks H and I being provided to withdraw the contents of thecompartments. The temperature of the solution is preferably kept at 6080C. When electric current is supplied the voltage between anode andcathode will be about 5 volts. During electrolysis a precipitation willtake place near the cathode E and at the same time the iron in thesolution will be deposited on the cathode. The precipitation consists ofaluminium hydrate containing small amounts of S0 in the form of adsorbedacid or a basic sulfate and is removed from the solution from time totime, subjected to washing and if pure A1 0 is desired is calcined,whereby the S0 is eliminated. The calcined product will contain lessthan 0.1% Fe O and is very well-adapted for the manufacture ofaluminium.

In the anode compartment free sulfuric acid is formed. This acid servesto dissolve the raw material, in this case pulverized labrodorite, whichis continuously added to the anode compartment, dissolution of the rawmaterial being facilitated by agitation.

When a considerable amount of undissolved residue has accumulated intheanode compartment electrolysis is interrupted. The anolyte is separatedfrom undissolved residue by means of filtration and the residue,principally consisting of SiO is rejected, the filtrate being returnedto the process but being in part poured into the cathode and part intothe anode compartment.

At the same time a part of the catholyteis removed and subjected tocrystallization in order to remove the salts which accumulate in thesolution. These are principally alkali salts, as the calcium present inthe raw material remains in the anode compartment in the form,of calciumsulfate, and crystallize out together with aluminium sulfate giving alumas a by-product.

The solution removed from the cathode compartment for crystallization isreplaced by a corresponding amount of the filtrate obtained from theanolyte. v

The anode compartment is then supplied 3 with sulfuric acid of such astrength that the H,SO,, contained therein will replace the H SO removedfrom the catholyte in the form of salts. The electrolysis is thencontinued as before.

eeaeoe The foregoing detailed description has been given for clearnessof understanding and no undue limitation should be deduced therefrom,but the appended claims should be construed as broadly as permissible inview of the prior art.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In the recovery of aluminium compounds, the process which compriseseffect-' ing precipitation thereby subjecting a solution containing analuminium mineralacid salt to electrolysis and thereby effectingprecipitation of an aluminium compound at the cathode.

2. In the recovery of aluminium compounds, the process which compriseseffecting precipitation thereof by subjecting a solution containing analuminium sulfate to electrolysis and thereby effecting precipitation ofa basic aluminium sulfate at the cathode.-

3. Tn the recovery of aluminium compounds, the process which comprisesefiecting precipitation thereof by subjecting a solution containing analuminium mineral acid salt to electroylsis in the presence of an alkalisalt and thereby effecting precipitation of an aluminium compound at thecathode.

4. In the recovery of aluminium compounds, the prooesswwhich compriseseffecting precipitation thereof by subjecting a s0- lution containing analuminium mineral acid salt to electrolysis in a diaphragm cell andthereby efi'ecting precipitation of an aluminium compound at thecathode.

5. In the recovery of aluminium compounds, the process which comprisesefiecting precipitation thereof by subjecting a so-. lution containingan aluminium sulfate to electrolysis in a diaphragm cell and therebyeffecting precipitation of a basic aluminium cipitation of an aluminiumcompound at the cathode.

8. In the recovery of aluminium compounds, the continuous process Whichcomprises efl'ecting precipitation thereof by subjecting a solutioncontaining an aluminium mineral acid salt to electrolysis in a dia-'phragm cell and thereby eifecting precipitation of an aluminium compoundat the cathode and liberation of the mineral acld at the anode, anddissolving at the anode by,

the liberated acid a substance containing combined alumlnlum.

9. In the recovery of alumlnlum comv pounds, the continuous processWhich comprises effecting precipitation thereof by subjecting a solutioncontaining aluminium sulfate to electrolysis in a diaphragm cell andthereby eifecting precipitation of a basic aluminium sulfate at thecathode andliberation of sulfuric acidat the anode, and dissolving atthe anode by the liberated sulfuric acid a substance containing combinedaluminium.

10. In the recovery of aluminium compounds, the continuous process whichcomprises effecting precipitation thereof by subjecting a solutioncontaining an aluminium mineral acid salt in the presence of an alkalisalt to electrolysis in a diaphragm cell and thereby efiectingprecipitation of an aluminium compound at the cathode and liberation ofthe mineral acid at the anode, and dissolving at the anode by theliberated acid a substance containing combined aluminium.

11. In'the recovery of aluminium compounds, the process Which consistsin making a solution of aluminium salt by subjecting a mineralcontaining combined aluminium to the action of a mineral acid,subjecting the solution so formed with the addition thereto of an alkalisalt to Vel'ectrolysis in a diaphragm cell having an insoluble anode,thereby efiecting pre-' clpitation of aluminium compound at the cathodeand liberation of the mineral acid at the anode, and dissolving at theanode by the liberated acid more of said mineral. Signed at Christiania,Norway, this 7th day of March, 1918.

MATHIAS OVROM SEM.

